The present invention relates to a sensor for measuring both the combustion pressure and the heat flow in the combustion chamber of an internal combustion engine, in particular, for motor vehicles. In addition to the combustion pressure, the heat flow through the engine block and the gas temperature in the combustion chamber are also of interest as a further thermodynamic variable. These variables are to be detected. Since the possibility of making additional bores in the engine block for additional sensors is highly restricted, a technical procedure is sought according to the teaching solving the present problem. The technical teaching indicated in the present invention solves the abovementioned problem. The invention is based on the object of integrating the heat-flow sensor in the provided pressure sensor which projects into the combustion chamber of the engine. The invention relates, but not in a restrictive manner, especially to pressure sensors as disclosed in the German Offenlegungsschriften DE-OS 3 714 131 and 3 727 221.
These known pressure sensors have as components which are of particular interest here a diaphragm whose one side delimits the combustion chamber of the engine and on whose opposite diaphragm surface a tappet or the like rests so that the pressure prevailing on the other side of the diaphragm can be transmitted as a force from this diaphragm surface to a sensor element of the pressure sensor. This sensor element is particularly a piezoelectric sensor, preferably in the form of a plate to be bent or a tube of piezo material to be loaded in the axial direction with the pressure. In particular piezo ceramic such as lead zirconate titanate and the like are used as piezoelectric material. This material is cheap and technically sophisticated.